The present invention relates to a gear shift mechanism.
From German Patent Document 39 274 C1, a transmission is known in which a first and a second shiftable gear wheel are rotatably disposed on an input shaft. Between the two gear wheels, a fixed sleeve is arranged which is non-rotatably connected with the input shaft. On the fixed sleeve, a sliding sleeve is axially displaceably arranged which can take up three shifting positions, specifically a center or neutral position as well as a first or second shifting position in which the first or second gear wheel is non-rotatably connected by way of the sliding sleeve and the fixed sleeve with the shaft. For operating the sliding sleeve, a groove is provided on its outer circumference into which a “displacement device”, that is, a shift fork engages which is connected with a shift rod and which can be operated by the driver by way of a gear shift lever.
As explained, for example, in the above-mentioned German Patent Document DE 39 274 C1, in gear change boxes without planetary gear trains, a gear is shifted in which an interlocking connection is established between a gear wheel and the assigned shaft. When the connection between the gear wheel and the shaft is closed, a torque can be transmitted by way of this “path”. Such a “connection element” has an interior part or a fixed sleeve, with an external toothing having teeth arranged in the axial direction, as well as an axially displaceable exterior part or a sliding sleeve, with an internal toothing having teeth also aligned in the axial direction. The interior part and the exterior part are in a constant engagement. As a result of an axial displacing of the sliding sleeve, a gear wheel can be connected, that is, can be connected with the shaft in the rotating direction in an interlocking manner by way of the fixed sleeve.
During the excursion from the neutral position, the sliding sleeve is moved so far in the axial direction that, on the one hand, it is still engaged with the fixed sleeve but, on the other hand, it also dips with its internal toothing into the assigned toothing of the component “to be coupled”.
The excursion of the sliding sleeve from its center or neutral position takes place, for example, by means of a so-called “shift rocker”. A shift rocker carries out a swinging motion about an axis which is perpendicular to the longitudinal axis of the sliding sleeve but which does not intersect with the longitudinal axis. The shift rocker has movably arranged rocker arms which engage in a ring groove extending around the outer circumference of the sliding sleeve and which, during a tilting or swinging motion of the shift rocker, displace the sliding sleeve in the axial direction.
As an alternative to a shift rocker, a so-called “shift fork” can be provided for operating the sliding sleeve. The shift fork is form-fittingly disposed on a shift rod used for its bearing and guidance. The shift fork engages in the ring groove extending around the outer circumference of the slicing sleeve, which causes a “taking-along” of the sliding sleeve during an axial displacement.
An axially displaceable shaft with a driving finger form-fittingly disposed thereon, which is indicated to be a so-called “shifting shaft”, normally moves the shift rocker or the shift rod with its shift fork out of the neutral position.
Applicants are internally aware of an automated gear shift mechanism which is based on a conventional gear shift mechanism, in which case, by means of hydraulic actuators, the shifting shaft can, on the one hand, be axially displaced and, on the other hand, be rotated for the selection of the shifting channel.
It is an object of the present invention to provide a shift mechanism which has a compact construction and an expanded functionality.
The basic principle of the invention consists of a gear shift mechanism with a “displacement device”, which can be operated by an actuator, for the actual displacing of a sliding sleeve, the actuator being connected by way of at least one joint with the displacement device. Such an “articulated connection” between the actuator and the “displacement device” permits a greater “freedom” with respect to the spatial arrangement of the actuator and thus a very compact construction.
In the case of a motor vehicle transmission, several shifting channels are normally situated side-by-side, to which one shift rocker or one shift rod respectively having a shift fork are assigned. Preferably, a separate actuator is assigned to each shifting channel, which permits a separate control of the shift rockers or shift rods and shift forks of the individual shifting channels. This has the advantage that, in certain operating situations, more than one gear “can start to be synchronized” simultaneously. Another advantage is the fact that several gears can be skipped without any problem and without unacceptably long shifting times. In addition, the disengaging of a gear and the engaging of another gear can take place in an overlapping manner without respect to time, which permits shorter shifting times.
However, in modern vehicle transmissions, the installation of several actuators frequently represents a space problem. The shift rods of the individual shifting channels are usually situated very closely side-by-side or the mutual spacing of the shift rockers is not sufficient for the installation of an actuator. As a result of the above-explained articulated connection of the actuator with their assigned “displacement device”, the space problem will be solved. The reason is that, as a result of the articulated connection, the actuators do not need to be arranged coaxially with respect to the individual shifting channels. Thus, several actuators can be arranged side-by-side without any problem.
According to the invention, two subvariants exist, specifically:                a) individual actuators are connected directly by way of a single joint with the displacement device; that is, the actuator piston is connected directly by way of the joint with the displacement device; and b) the actuator or the actuator piston is connected by way of an intermediate element and two joints with the displacement device.        
The articulated connection permits different actuator arrangements. In the case of the variant a) with a joint, the actuator may be arranged diagonally with respect to the shifting channel. In the case of the variant b) with two joints and an intermediate element, the actuator can be arranged to be offset in parallel with respect to the shifting channel.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.